1. Field of the Invention
The present invention relates to protection devices, and more particularly to conduit shields used to protect conduits in various heat-exchanger apparatuses, such as boilers and condensers. The present invention is further related to boiler tube shields for protecting tubes from the hostile environment in a boiler, for example, from corrosive or abrasive soot or fly ash in a fossil fuel boiler.
2. Description of Related Art
Conduits are hollow, elongated casings for which liquid, gas and the like can flow therethrough. Conduits, such as tubes and pipes, are often used in various heat exchanger apparatuses, for example, boilers and condensers for heating a medium, such as water. Unfortunately, tubes employed in a boiler, particularly a fossil fuel boiler, are typically exposed to hostile elements, such as soot, fly ash, extreme heat, soot blower steam, or combinations thereof. The hostile elements will eventually take their toll on the tubes via corrosion or abrasion of the exterior wall, such that the wall of one or more tubes may over time lose its integrity and eventually fail, resulting in major maintenance and significant boiler downtime costs.
Conduit shields, often referred to as tube shields, were designed to protect the boiler conduits from the harsh environment within the boiler. Specifically, the conduit shield protects a portion of the exterior wall of the tube of the conduit.
For instance, conventional tube shields are axially-elongated protector members having a cross-section that is sized to fit over a tube to protect the integrity of the tube from the boiler environment. Most boiler tube shield designs require that the shield be welded to the tube that it protects. But the welding process can be unsafe, time-consuming, expensive, and require specialized tools and training. In addition, welding is a permanent attachment process that requires great effort to reverse should the tube shield require adjustment or removal.
Referring to FIGS. 1-3, a conventional, exemplary system of heating water in a boiler environment 100 is illustrated. Water flows through the conduit, or tube, 105. In the boiler environment 100, it is desired that the water be heated, so heated boiler gas 110 is forced past the tube 105 to heat the water in the tube 105.
Typically, the boiler gas 110 contains particulates 115. Oftentimes, the particulates 115 come from combustion boxes of the boiler environment 100. Soot or ash, which is essentially matter that will not burn, is an exemplary particulate in the boiler gas 110 in the boiler environment 100. The heated boiler gas 110 containing particulates 115 is forced by the tube 105 and causes the ash particulate 115 to move at a high velocity. As a result, the particulates 115 can strike the tube and/or adhere thereto, which over time erodes the wall 105w of the tube 105. When ash and other particulates accumulate on the outside wall 105w of the tube 105, as shown in FIG. 3, high pressure steam can be used to clean same. Unfortunately, high pressure steam can also include particulates (e.g., water particulate), which can also damage the wall 105w of the tube 105.
Thus, in order to protect the tube 105, a shield 200 has conventionally been attached to the outside wall 105w of the tube 105. A perspective view of a conventional shield 200 is illustrated in FIG. 4. Conventional shields 200 include a body 205 for protecting the tube 105, and a band 210 for securing the body 205 to the tube 105. Conventional shields 200 are welded to the tube 105 in the path of the particulates by the band 210. Weld points 215 are the connection between the band 210 and the body 205. FIG. 5 illustrates the conventional shield 200 secured to the tube 105.
Unfortunately, the weld points 215 are typically the first to erode because they are in the direction of the gas flow, for example see Arrow A of FIG. 5. Ultimately over time, the weld points 215 fail because the particulates 115 strike the weld point, and hence it becomes compromised. As a result, the weld fails and the shield 200 falls off the tube. Further, because conventional shields 200 are solely held in place by the welded band, there is a likelihood that over time the shield 200 will shift either axially (along the length of the tube) or rotationally (around the tube).
Therefore, what is needed is an improved tube shield assembly overcoming the deficiencies of the prior art. It is to such a device that the present invention is primarily directed.